[time-nuts] webcam app to watch for and time stamp changes
cfharris at erols.com
Sun Mar 3 21:34:22 EST 2013
In the watchmaker world, we have error, and personal error.
The watchmaker sets the watch to get the most accurate time
while sitting in his shop, and then he gives the watch to the
customer with the instructions to wear the watch normally for
2 weeks, but don't reset it, and bring it back for adjustment.
The watchmaker carefully checks the time, and makes note of
the error from real time. He then adjusts the watch to run,
at normal shop temperature, to run at -1 times the error...
in other words, if the watch is 2 minutes fast over two weeks,
he adjusts so that it will be 2 minutes slow over two weeks...
at normal shop temperature.
The customer takes his watch, and marvels at how extremely
accurate it is.
The lesson to be learned is set the LCD watch using the counter,
at normal shop temperature. Give it to the customer to wear
for two weeks. Calculate the error rate, and then readjust the
watch for -1 times that error rate at normal shop temperature.
-Chuck Harris (amateur watchmaker)
> When LCD wristwatches became common in the seventies we, in the frequency and timing
> group of a space tracking facility, investigated the possibility of adjusting our new
> watches against our standard.
> We found that a a small copper plate, about 1 X 2 cm, resting against the display and
> connected to a scope probe was able to pick up enough 32 KHz energy to be displayed
> in the scope. Then connected the vertical output to an HP 5245L counter referenced
> to our standard and set the gate time to 10 seconds and got the frequency. We
> learned that the watch had to be worn in order to operate at the right temperature,
> the body acting as an oven, so you has to wear it backside in order to access the
> trimmer (yes, at that time those watches had and adjusting trimmer, maybe heritage
> from the mechanical ones, laser trimming arrived later).
> Our group became very popular and busy adjusting every watch our colleagues bought to
> a few seconds per month.
> Ignacio, EB4APL
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